The accepted unit of measurement for long books is War and Peace. Library shelves bend and buckle under the weight of bigger doorstops, but it's Tolstoy's classic that has become the shorthand for a hefty tome.

At 2.6 million words, the Iraq Inquiry Report will be four and half times longer than War and Peace.

We know the figure because Sir John Chilcot, the inquiry chairman, made pointed reference to it in his letter to David Cameron announcing his intention to publish it on Wednesday.

Sir John began the inquiry seven years ago and has become increasingly frustrated by ever-louder criticism of the length of time it has taken to interview witnesses and prepare the report.

These things can't simply be dashed off, he was reminding the Prime Minister. He might have added – but didn't – that Tolstoy laboured on War and Peace for 12 years before it was finally published in full.

The frustration felt by of relatives of the 179 British service personnel who died in Iraq between 2003 and 2009 is even more understandable.

But questions and complaints about the time it has taken to examine the UK's role in the Iraq war are now largely academic. We will know the conclusions in a few days' time.

It seems strange to think there is a story guaranteed to top Brexit fallout on the front pages in the TV news bulletins but there is, and this is it. It's worth reminding ourselves, then, what the inquiry has been doing these past seven years, at a cost of £10.4 million.

It was announced by then-prime minister Gordon Brown in 2009, shortly after the last British troops left Iraq.

It has examined, in painstaking detail, the period 2001 and 2009, covering the decision to join the US-led invasion of Iraq, the preparedness of British troops, the military campaign itself and what plans were made for the country after Saddam Hussein was toppled.

Inevitably, the list of witnesses reads like a Who's Who of the Establishment.

Tony Blair, who led Britain to war and whose dealing with former UK president George W Bush are at the heart of the inquiry, twice gave evidence.

Other witnesses included Mr Brown, Chancellor at the time of the invasion; the then-Foreign Secretary Jack Straw; Defence Secretary Geoff Hoon; International Development Secretary Clare Short, and Attorney General Lord Goldsmith, who advised ministers the war was lawful.

They were joined by diplomats, senior civil servants and military commanders.

Questioning focused on Mr Blair's discussions with Mr Bush in the run-up to 2003, the evidence behind the "dodgy dossier" on Saddam's alleged – but non-existent – weapons of mass destruction, the legal justification for war and the role of the United Nations.

Describing the inquiry's purpose, Sir John said it would attempt "to establish, as accurately as possible, what happened and to identify the lessons that can be learned".

From the outset, he has talked of helping future governments learns from the lessons of history.

The inquiry is not a court of law and nobody is on trial, he has been at pains to stress – though he has promised to point the finger of blame where necessary.

The question for many people, however, is the one Peter Oborne, the columnist and political commentator, asks in his book Not the Chilcot Report: Is Tony Blair a war criminal?

Those 2.6 million words will be scoured first on Wednesday morning for the inquiry's view on whether the former prime minister had given President Bush assurances about Britain's commitment to overthrowing Saddam regardless of whether the tyrant possessed WMDs.

Oborne answers his own question in the affirmative. Mr Blair, he argues, could "reasonably be accused" of committing the supreme international crime, that of initiating a war of aggression, as defined during the Nuremberg trials that followed the Second World War. However, he does not believe Mr Blair will be prosecuted as the International Criminal Court (ICC) based in The Hague, has no jurisdiction over the crime of aggression.

Alex Salmond, the former SNP leader who opposed the war in 2003, has reached a similar conclusion and believes the Chilcot report will provide the proof. Unlike Oborne, he remains hopeful of a prosecution in the ICC.

Learning the lessons of history may well be uppermost in Sir John's mind when he presents his report on Wednesday. Depending on the findings, however, others will be looking for justice.